Method and system for measuring latency

ABSTRACT

A system and method for measuring latency of an optical transport network includes generating a time stamp, transmitting the time stamp in an optical transport network, and processing the time stamp to measure latency of the optical transport network.

CROSS-REFERENCE TO RELATED APPLICATIONS

This present patent application is a continuation of U.S. patentapplication Ser. No. 11/693,211, filed Mar. 29, 2007, entitled “METHODAND SYSTEM FOR MEASURING LATENCY” to Michael B. Freiberger. Thedisclosure of this priority application is hereby incorporated byreference herein in its entirety.

BACKGROUND

Communication networks of today often provide communication viadigitally wrapped packet transmissions. There are many framedcommunication protocols in use and these protocols may be arbitrary orsupported by an underlying function. A communication network may haveone or more nodes which may transfer data streams over a communicationchannel. Many applications enabled by such a communication network maybe latency sensitive and therefore may require a particular latency.However, latency measurement within a communication network may bedisruptive of the transmission of data. Oftentimes, personnel may berequired to test latency, thereby further complicating the process.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to facilitate a fuller understanding of exemplary embodiments,reference is now made to the appended drawings. These drawings shouldnot be construed as limiting, but are intended to be exemplary only.

FIG. 1 illustrates an exemplary optical transporting network system,according to an exemplary embodiment.

FIG. 2 illustrates an exemplary system to measure the latency of anoptical transporting network system, according to an exemplaryembodiment.

FIG. 3 illustrates an exemplary standard interface for an opticaltransporting network system, according to an exemplary embodiment.

FIG. 4 illustrates an exemplary overhead area of an interface for anoptical transporting network system, according to an exemplaryembodiment.

FIG. 5 illustrates an exemplary detailed overhead area of an interfacefor an optical transporting network system, according to an exemplaryembodiment.

FIG. 6 is a flow chart illustrating an exemplary process of measuringthe latency of an optical transporting network system, according to anexemplary embodiment.

FIG. 7 is a flow chart illustrating an exemplary process of measuringthe latency of a synchronized optical transporting network system,according to an exemplary embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

An exemplary embodiment of the present invention provides a system andprocess for monitoring delay within a network system. In one embodimentof the present invention, the network system may include synchronizednetwork elements to facilitate measurement of latency of the networksystem. For example, latency of a network may refer to measurement ofone-way latency which measures the time from a source transmitting datato a destination receiving the data. Latency of a network may also referto the measurement of round-trip latency which measures one-way latencyfrom a source to a destination plus one-way latency from the destinationback to the source.

Latency measurement for an Optical Transport Network may have variousapplications. For example, a predetermined latency measure between twonodes may be established as a default latency measure between two nodes.A variance in latency measure from the default latency measure betweenthe two nodes in an Optical Transport Network may indicate with a changein the length of telecommunication line linking the two nodes. Also, avariance in latency measure from between two nodes in an OpticalTransport Network may indicate certain events. For example, an illegaltapping by an entity may cause a delay in the Optical Transport Networkand thus may lead to a variance in the latency measure. Other variousapplications associated with latency measure for an Optical TransportNetwork may be implemented.

FIG. 1 is an exemplary network system, according to an exemplaryembodiment. System 100 illustrates an exemplary system for an OpticalTransport Network (OTN) which may implement a variety of standards ofinterface for managing optical wavelengths. For example, variousstandards of interface for managing the transmission of data within anOptical Transport Network may include a synchronous digital hierarchystandard (SDH) developed by the International Telecommunication Union(ITU), a synchronous optical networking (SONET) standard developed byTelcordia Technologies and/or other standards. A standard developed bythe international Telecommunication Union is G.709 which may enable theuse of optical switches without the optical/electrical/optical (O/E/O)conversions while compensating for data corruption due to impurities inoptical equipments of the Optical Transport Network (OTN). In anexemplary embodiment, ITU-T G.709, a standard recommended by theInternational Telecommunication Union Telecommunication StandardizationSector may be used to enable the management of optical wavelength in anOptical Transport Network (OTN). Other Standards may also beimplemented.

As illustrated, System 100 may include a plurality of Nodes 101 coupledby a network of Telecommunications Links 102. A network of Nodes 101 andTelecommunication Links 102 may be arranged to enable transmission ofdata from a source node to a receiving node over a single or multipletelecommunication links. For example, a transmission of data from Node 1to Node 2 as illustrated in FIG. 1 may be enabled by transmission viaplurality of intermediate Node 10 and Node 12 and/or Node 9 and Node 11.Various different paths of transmission between a source node and atermination node may be enabled by different intermediate nodes withinthe Optical Transport Network (OTN).

Node 101 may be a source node where transmission of data commences, atermination node where transmission of data terminates, and/or anintermediate node where transmission of data may traverse. Node 101 mayimplement various network elements to enable transmission of databetween each node.

Telecommunication Link 102 may be a communication channel that mayconnect two or more network elements. Telecommunication Link 102 may bea physical telecommunication link or multiple of physicaltelecommunication links or a logical telecommunication link.Telecommunication Link 102 may be a point-to-point link, a multipointlink, a point-to multipoint link, or a combination of different types oflinks mentioned before. In an exemplary embodiment, an optical fiber mayinclude glass and/or plastic fiber to guide light may be used forTelecommunication Link 102. Various types of optical fiber may be usedfor Telecommunication Link 102 which may include, without limitation,multi-mode optical fibers, single-mode optical fibers, graded-indexfibers, step-index optical fiber or a combination of the different typesof optical fiber mentioned before.

FIG. 2 illustrates an exemplary system 200 for measuring the latency ofan Optical Transporting Network (OTN), according to an exemplaryembodiment. Latency measuring system 200 may include a Source Node 201and/or one or more Intermediate/Termination Node 202. Source Node 201may represent a node sending a data packet. Intermediate/TerminationNode 202 may represent a node receiving a data packet. In an exemplaryembodiment, Source Node 201 may include a Time Stamp Module 210, aTransmission/Receiving Module 212, a Processing Module 214 and/or OtherModule 216. Source Node 201 may communicate withIntermediate/Termination Node 202 via one or more links, as shown byTelecommunication Link 102. Intermediate/Termination Node 202 mayinclude a Time Stamp Module 220, a Transmission/Receiving Module 222, aProcessing Module 224 and/or Other Module 226. Each node may includeadditional modules, as shown by Other Module 216 and 226. In addition,the modules at each node may be combined, duplicated, separated and/orotherwise modified based on various applications and preferences. Otherarchitectures and implementations may be realized.

In an exemplary embodiment, Source Node 201 may initiate a process formeasuring latency of an Optical Transporting Network (OTN). Time StampModule 210 of Source Node 201 may generate a first time stamp such as acounter, trusted time stamp, digital postmark, digital time stamp and/orany signal or algorithms which may keep time. The first time stamp maybe associated with a time tracking device at Source Node 201. The timetracking device may include one or more various types of time trackingdevices and/or a clock network which may enable time synchronization ateach node of the Optical Transporting Network (OTN).

The first time stamp may be transmitted to Transmission/Receiving Module212 where Transmission/Receiving Module 212 may associate the first timestamp with an Optical Transport Unit (OTU) frame. Further,Transmission/Receiving Module 212 of Source Node 201 may transmit theOptical Transport Unit (OTU) frame with the associated first time stampto Transmission/Receiving Module 222 at Intermediate/Termination Node202.

Transmission/Receiving Module 222 may receive the Optical Transport Unit(OTU) frame with the associated first time stamp and extract the firsttime stamp from the Optical Transport Unit (OTU) frame. The extractedfirst time stamp may be transmitted to and/or stored in ProcessingModule 224, Processing Module 224 may include a processing unit, astorage unit and/or other various network elements. Processing Module224 may include various storage elements to store the first time stamp.In addition, Processing Module 224 may determine one-way latency of theOptical Transporting Network (OTN) based on the information associatedwith the first time stamp. Further, Processing Module 224 may includewithout limitation, software, hardware or a combination of software andhardware operable to determine the latency of an Optical TransportNetwork (OTN). In addition, the software may include, withoutlimitation, algorithms determining latency in an Optical TransportNetwork (OTN). The hardware may include, without limitation, a processorand/or other similar integrated circuit.

Time Stamp Module 220 at Intermediate/Termination Node 202 may accessthe first time stamp stored in Processing Module 224 and generate asecond time stamp such as a counter, trusted time stamp, digitalpostmark, digital time stamp and/or any signal or algorithms which maykeep time. The second time stamp may be associated with the first timestamp. Also, the second time stamp may be associated with a timetracking device located at Intermediate/Termination Node 202. The timetracking device may include one or more various types of time trackingdevices and/or a clock network which may enable time synchronization ateach node of the Optical Transporting Network (OTN).

Time Stamp Module 220 may transmit the second time stamp toTransmission/Receiving Module 222. Transmission/Receiving Module 222 mayassociate the second time stamp in an Optical Transport Unit (OTU) frameand transmit the Optical Transport Unit (OTU) frame with the associatedsecond time stamp to Transmission/Receiving Module 212 at Source Node201.

Transmission/Receiving Module 212 may receive the Optical Transport Unit(OTU) frame with the associated second time stamp and extract the secondtime stamp from the Optical Transport Unit (OTU) frame. The extractedsecond time stamp may be transmitted to and/or stored in ProcessingModule 214. Processing Module 214 may include a processing unit, astorage unit and/or other various network elements. Processing Module214 may include various storage elements to store the second time stamp.In addition, Processing Module 214 may determine latency of an OpticalTransporting Network (OTN) based on the information associated with thesecond stamp. Further, Processing Module 214 may include withoutlimitation, software, hardware or a combination of software and hardwareoperable to determine latency of an Optical Transport Network (OTN). Inaddition, the software may include, without limitation, algorithmsdetermining latency in an Optical Transport Network (OTN). Further, thehardware may include, without limitation, a processor and/or othersimilar integrated circuit.

Furthermore, Other Module 216, 226 may include various types of networkelements in cooperation with other modules at each node to enable aprocess to measure latency of an Optical Transporting Network (OTN).

FIG. 3 illustrates an exemplary Optical Transport Unit (OTU) frame,according to an exemplary embodiment. In this exemplary embodiment, theITU-T G.709 standard may apply. The various embodiments of the presentinvention may apply to other standards as well. As illustrated in FIG.3, an Optical Transport Unit (OTU) frame may include an Overhead 301 foroperation, administration, and/or maintenance functions, a Payload 302for data storage during a transmission and/or Forward Error Correction303 which may reduce the number of transmission errors on noisy linkswhile enabling the deployment of longer optical spans. Further, ForwardError Correction 303 may include a Reed-Solomon (RS) code to produceredundant information which may be concatenated with the signal to betransmitted. The redundant information generated by the Reed-Solomon(RS) code may enable a receive interface to identify and/or correct anytransmission errors.

According to an exemplary embodiment, an Optical Transport Unit (OTU)frame for ITU-T G.709 network interface standard may include four rowsof 4080 bytes. Data may be transmitted serially beginning at the topleft, first row, and may be followed by the second row and so on. TheITU-T G.709 network interface standard may enable three rates of datatransmission, for example, 2,666,057.413 kbit/s—Optical ChannelTransport Unit 1 (OTU1) which may have a frame rate of 20.420 kHz or48.971 ms, 10,709,225.316 kbit/s—Optical Channel Transport Unit 2 (OTU2)which may have a frame rate of 82.027 kHz or 12.191 ms, or43,018,413.559 kbit/s—Optical Transport Channel Unit 3 (OTU3) which mayhave 329.489 kHz or 3.035 ms.

FIG. 4 illustrates details for an exemplary Overhead 301 of an OpticalTransport Unit (OTU) frame, according to an exemplary embodiment. Inthis exemplary embodiment, the ITU-T G.709 standard may apply. FIG. 4illustrates general exemplary components for Overhead 301 of an OpticalTransport Unit (OTU) frame for ITU-T G.709 network interface standard.Overhead 301 may include a Frame Alignment Overhead 401, Optical ChannelTransport Unit (OTU) Overhead 402, Optical Channel Data Unit (ODU)Overhead 403 and/or Optical Channel Payload Unit (OPU) Overhead 404.

FIG. 5 illustrates detailed exemplary components for Overhead 301 of anOptical Transport Unit (OTU) frame. Frame Alignment Overhead 401 mayenable a receiving network element of an Optical Transport Network (OTN)frame to identify a starting point by framing bytes. Frame AlignmentOverhead 301 may include a 6-bytes frame alignment signal (FAS) in row 1columns 1-6. A frame alignment signal (FAS) may enable a receivingnetwork element to identify any out-of-frame (OOF), loss-of-frame (LOF)and/or a start of an Optical Transporting Unit (OTU) frame. In anexemplary embodiment, Overhead 301 may include signals which may spanmultiple Optical Transport Unit (OTU) frames therefore, Frame AlignmentOverhead 401 may include a multi-frame alignment signal (MFAS) byte toidentify signals that may span multiple Optical Transport Unit (OTU)frames. The multi-frame alignment signal (MFAS) for Frame Alignment Overhead 301 may be defined in row 1 column 6 and/or 7.

Optical Channel Transporting Unit (OTU) Overhead 402 may be located atrow 1 columns 8-14, which may provide supervisory functions. OpticalChannel Transport Unit (OTU) Overhead 402 may include three bytessection monitoring (SM), two-byte general communications channel (GCC0),and two bytes reserved for future international standardization. Thesection monitoring (SM) of Optical Channel Transporting Unit (OTU)Overhead 402 may test and/or monitor Overhead Area 301 and/or PayloadArea 302. The general communications channel (GCC0) may be defined inrow 1 columns 11 and 12 which may provide control of a channelconnection between Optical Transport Unit (OM) frame termination pointsand/or network management. Optical Channel Transporting Unit (OTU)Overhead 402 may further include a reserved (RES) field located in row 1column 13 and 14 which may be set aside for future standardization.

Optical Channel Data Unit (ODU) Overhead 403 may reside in rows 2, 3 and4 of column 1-14 of the Optical Transporting Network (OTN) frame.Optical Channel Data Unit (ODU) Overhead 403 may include multiple tandemconnection monitoring (TCM), which may enable a network operator tomonitor the transmission of a signal. Optical Channel Data Unit (ODU)Overhead 403 may also include TCM activation (TCM ACT) field which mayenable the activation and/or deactivation of tandem connectionmonitoring (TCM) channels. Optical Channel Data Unit (ODU) Overhead 403may further include path monitoring (PM) which may function in a similarmanner as the section monitor in the Optical Channel Transporting Unit(OTU) Overhead 402 described above except the path monitoring (PM) mayprovide end-to-end monitoring. Furthermore, Optical Channel Data Unit(ODU) Overhead 403 may include a fault type and fault location (FTFL)which may monitor path level faults, transport both forward and backwardfault information and/or a message structure. Moreover, Optical ChannelData Unit (ODU) Overhead 403 may include general communications channelfields GCC1 and GCC2 which may provide clear channel connection betweenOptical Channel Data Unit (ODU) termination points. In addition, OpticalChannel Data Unit (ODU) Overhead 303 may include two reserved (RES)fields which may be used for future standardization and may be locatedin row 2 column 1-3 and row 4 columns 9-14.

Optical Channel Payload Unit (OPU) Overhead 404 may includejustification control (JC) located in column 15 row 1, 2 and 3. Thejustification control (JC) byte provide for payload movements inside theOptical Transport Network (OTN) frame. Optical Channel Payload Unit(OPU) Overhead 404 may include three justification control bytes wheretwo out of three justification controls may be sufficient to carry outjustification events. Two types of justification control (JC) maydetermine a justification event, for example, a positive justificationopportunity (PJO) and/or a negative justification opportunity (NJO). Apositive justification opportunity (PJO) may cause one of payload bytesto not contain payload information as a justification event may occur. Anegative justification opportunity (NJO) may cause one of payload bytesto temporarily maintain payload information as a justification even mayoccur. Optical Channel Payload Unit (OPU) Overhead 404 may includepayload structure identifier (PSI) which may include payload type (PT)to identify the payload content. The payload structure identifier (PSI)may include one-byte located in row 4, column 15 to transport a 256-bytepayload structure identifier (PSI) signal. The payload type (PT) and/orvirtual concatenation payload type (vcPT) may be each represented byone-byte in the 256-byte of payload structure identifier (PSI). The rest254-bytes of payload structure identifier (PSI) may be reserved forfuture international standardization.

In an exemplary embodiment, a time stamp may be associated with anOptical Transporting Unit (OTU) frame. The time stamp may be insertedwithin an Overhead 301 of an Optical Transporting Unit (OTU) frame. Thesize of a time stamp may vary. For example, amount, size or type ofinformation associated with the time stamp may affect the size of thetime stamp. In addition, other factors may be considered. Therefore, atime stamp may be inserted within different locations of Overhead 301depending on the characteristics, size, amount, type, etc., of the timestamp. In an exemplary embodiment, a time stamp may be inserted in FrameAlignment Overhead 401, Optical Channel Transporting Unit (OTU) Overhead402, Optical Channel Data Unit Overhead 403 and/or Optical ChannelPayload Unit Overhead 404. For example, a time stamp may be insertedwithin Frame Alignment Overhead 401, wherein a reserved space may beavailable in a frame alignment signal (FAS) and/or a multi-framealignment signal (MFAS). Also, a time stamp may be inserted within areserved space in Optical Channel Transport Unit (OTU) Overhead 402located at row 1 columns 13 and 14. Further, a time stamp may beinserted within a reserved space in Optical Channel Data Unit (ODU)Overhead 403 located at row 2 columns 1, 2 and 3, and/or row 4 columns9, 10, 11, 12, 13 and 14. Furthermore, a time stamp may be insertedwithin a reserved space in Optical Channel Payload Unit (OPU) Overhead304 located at column 15 rows 1, 2, 3 and 4 and/or column 16 rows 1, 2,3 and 4. Moreover, a time stamp may be inserted in any reserved spacelocated in column 17. An Optical Transporting Unit (OTU) frame withinserted time stamp may be transmitted over an Optical TransportingNetwork (OPN) to an intermediate and/or termination node. In addition,information associated with the time stamp may be spread across multiplelocations. Other various locations may be used for the time stamp.

In an exemplary embodiment, the ITU-T G.709 network interface standardmay enable virtual concatenation which may enable a channel within agroup to travel on different physical paths through an Optical TransportNetwork (OTN). Virtual concatenation (VOCH) overhead which may bespecific in each individual Optical Transport Unit (OTU) frame. OpticalChannel Payload Unit (OPU) Overhead 304 may include three-byte ofvirtual concatenation overhead (VCOH) which may be located at column 15,row 1, 2 and 3. Three bytes per individual Optical Channel Payload Unit(OPU) Overhead 304 may be utilized to transport a 3 byte×32 framestructure for virtual concatenation specific overhead. The virtualconcatenation overhead (VCOH) for the Optical Channel Payload Unit (OPU)Overhead 404 may also include a reserved field for future internationalstandardization.

FIG. 6 is a flow chart 600 which illustrates an exemplary method ofmeasuring latency of an Optical Transporting Network (OTN). At block601, a time stamp module may generate a first time stamp. The first timestamp may correspond to a time tracking device associated with a sourcenode.

At block 602, the first time stamp may be associated with an OpticalTransporting Unit (OTU) frame and transmitted to anintermediate/termination node. For example, the first time stamp may beinserted within an Overhead Area of an Optical Transport Unit (OTU)frame as mentioned above.

At block 603, a transmission/receiving module at anintermediate/termination node may receive the Optical Transporting Unit(OTU) frame with the associated first time stamp. Thetransmission/receiving module at the intermediate/termination node mayextract the first time stamp from an Overhead Area of the OpticalTransporting Unit (OTU) frame.

At block 604, the transmission/receiving module at theintermediate/termination node may transfer the extracted first timestamp to a processing module at the intermediate/termination node. Theprocessing module may store the first time stamp in a storage unit.

At block 605, a time stamp module at the intermediate/termination nodemay access a storage unit associated with the processing module toobtain information associated with the first time stamp. The time stampmodule at the intermediate/termination node may generate a second timestamp associated with the information of the first time stamp.

At block 606, the second time stamp generated at theintermediate/termination node may be associated with an OpticalTransporting Unit (OTU) frame and transmitted back to the source node.For example, the second time stamp may be inserted within an OverheadArea of an Optical Transport Unit (OTU) frame as mentioned above.

At block 607, the transmission/receiving module at the source node mayreceive the Optical Transporting Unit (OTU) frame with the associatedsecond time stamp. For example, the transmission/receiving module at thesource node may extract the second time stamp from an Overhead Area ofthe Optical Transporting Unit (OTU) frame.

At block 608, a processing module may store the second time stamp. Theprocessing module may also determine the latency of an OpticalTransporting Network. The second time stamp may include informationassociated with the first time stamp. For example, the information mayinclude the time when the first time stamp may have been generatedand/or transmitted. The processing module may determine the amount oftime elapsed from the time the first time stamp may be generated and/ortransmitted to determine the latency of the Optical Transporting Network(OTN). Also, the second time stamp may include a time counter or othertime tracking device. The time counter may increment by a predeterminedperiod of time. Accordingly, the processing module may determine latencyof the Optical Transporting Network (OTN) based on the increment of thetime counter.

In an exemplary embodiment, transmission between a source node and atermination node may traverse through one or more intermediate nodesalong a transmission path. The one or more intermediate nodes may enablepassage of an Optical Transport Unit (OTU) frame with the associatedtime stamp. Also, an intermediate node may generate one or moreintermediate time stamps at each intermediate node according to theprocess mentioned above and transmit one or more intermediate timestamps to a subsequent intermediate node.

FIG. 7 depicts a flow chart 700 which illustrates an exemplary method ofmeasuring the latency of a synchronized Optical Transporting Network(OTN). At block 701, the time at a plurality of nodes in an OpticalTransporting Network (OTN) may be synchronized. For example, a clocknetwork may enable the plurality of nodes to display the same orsynchronized time. Also, the time for the node at two end points of atransmission and/or any intermediate nodes along a transmission path maybe synchronized. The plurality of nodes may be synchronized by settingthe source node as a default/master clock while a termination nodeand/or one or more intermediate nodes may be a slave clock which maydisplay the time of the master clock. Further, the nodes may besynchronized by setting an arbitrary node in the Optical TransportNetwork (OTN) as a master clock while a source, a termination, and/or anintermediate node may be a slave clock which may display the time of themaster clock.

At block 702, a time stamp module may generate a first time stamp. Thefirst time stamp generate may correspond to a time tracking deviceassociated with a source node.

At block 703, the first time stamp may be associated with an OpticalTransporting Unit (OTU) frame and transmitted to anintermediate/termination node. For example, the first time stamp may beinserted within an Overhead Area of an Optical Transport Unit (OTU)frame as mentioned above.

At block 704, a transmission/receiving module at anintermediate/termination node may receive the Optical Transporting Unit(OTU) frame with the associated first time stamp. Thetransmission/receiving module at the intermediate/termination node mayextract the first time stamp from an Overhead Area of the OpticalTransporting Unit (OTU) frame.

At block 705, the transmission/receiving module at theintermediate/termination node may transfer the extracted first timestamp to a processing module at the intermediate/termination node. Theprocessing module may store the first time stamp in a storage unit.

At block 706, a time stamp module at the intermediate/termination nodemay access a storage unit associated with the processing module toobtain information associated with the first time stamp. The time stampmodule at the intermediate/termination node may generate a second timestamp associated with the information of the first time stamp.

At block 707, the second time stamp generated at theintermediate/termination node may be associated with an OpticalTransporting Unit (OTU) frame and transmitted back to the source node.For example, the second time stamp may be inserted within an OverheadArea of an Optical Transport Unit (OTU) frame as mentioned above.

At block 708, the transmission/receiving module at the source node mayreceive the Optical Transporting Unit (OTU) frame with the associatedsecond time stamp. For example, the transmission/receiving module at thesource node may extract the second time stamp from an Overhead Area ofthe Optical Transporting Unit (OTU) frame.

At block 709, a processing module may store the second time stamp. Theprocessing module may also determine the latency of an OpticalTransporting Network. The second time stamp may include informationassociated with the first time stamp. For example, the information mayinclude the time when the first time stamp may have been generatedand/or transmitted. The processing module may determine the amount oftime elapsed from the time the first time stamp may be generated and/ortransmitted to determine the latency of the Optical Transporting Network(OTN). Also, the second time stamp may include a time counter or othertime tracking device. The time counter may increment by a predeterminedperiod of time. Accordingly, the processing module may determine latencyof the Optical Transporting Network (OTN) based on the increment of thetime counter.

In the preceding specification, various preferred embodiments have beendescribed with reference to the accompanying drawings. It will, however,be evident that various modifications and changes may be made thereto,and additional embodiments may be implemented, without departing fromthe broader scope of the invention as set forth in the claims thatfollow. The specification and drawings are accordingly to be regarded inan illustrative rather than restrictive sense.

The invention claimed is:
 1. A method, comprising: a second locationreceiving a first time stamp associated with a first location, whereinthe first time stamp was inserted into one of a frame alignment overheadportion, an optical channel transporting unit overhead portion, anoptical channel data unit overhead portion, and an optical channelpayload unit overhead portion of a first overhead of a first opticaltransport unit frame based on at least a characteristic of the firsttime stamp, wherein the characteristic of the first time stamp is atleast one of a size of the first time stamp, an amount of the first timestamp and a type of the first time stamp; extracting information of thefirst time stamp from the first overhead of the first optical transportunit frame; generating a second time stamp based at least in part on theextracted information of the first time stamp associated with the firstlocation, wherein the second time stamp includes at least part of theextracted information of the first time stamp; and transmitting thesecond time stamp in a second overhead of a second optical transportunit frame to the first location wherein the second time stamp is usedto measure a round trip delay of a network.
 2. The method according toclaim 1, wherein generating the second time stamp comprises generating asecond time counter.
 3. The method according to claim 2, whereingenerating the second time counter is associated with the first timestamp.
 4. The method according to claim 1, wherein the transmission ofthe second time stamp comprises associating the second time stamp with adigital wrapping circuit.
 5. The method according to claim 4, furthercomprises the second time stamp associated with an overhead portion ofthe digital wrapping circuit.
 6. A method, comprising: generating afirst time stamp associated with the first location; transmitting thefirst time stamp associated with the first location inserted into one ofa frame alignment overhead portion, an optical channel transporting unitoverhead portion, an optical channel data unit overhead portion, and anoptical channel payload unit overhead portion of a first overhead of afirst optical transport unit frame based on at least a characteristic ofthe first time stamp to a second location via a network, wherein thecharacteristic of the first time stamp is at least one of a size of thefirst time stamp, an amount of the first time stamp and a type of thefirst time stamp; receiving a second time stamp associated with thesecond location in a second overhead of a second optical transport unitframe, wherein the second time stamp includes at least part ofinformation of the first time stamp extracted from the first overhead ofthe first optical transport unit frame; and processing the second timestamp associated with the second location to measure a round trip delayof the network.
 7. The method according to claim 6, wherein generatingthe first time stamp associated with a first location comprisesgenerating a time counter.
 8. The method according to claim 6, whereintransmitting the first time stamp associated with the first locationcomprises associating the first time stamp with the first location in adigital wrapping circuit.
 9. The method according to claim 6, furthercomprises associating the first time stamp with the first location in anoverhead portion of the digital wrapping circuit.
 10. The methodaccording to claim 8, wherein processing the second time stampassociated with the second location further comprises: determining theround trip delay of the network based at least in part on the secondstamp associated with the second location.
 11. The method according toclaim 6, further comprises: synchronizing network elements at the firstlocation and the second location.
 12. A system, comprising: a receivingmodule at a second location to receive a first time stamp associatedwith a first location inserted into one of a frame alignment overheadportion, an optical channel transporting unit overhead portion, anoptical channel data unit overhead portion, and an optical channelpayload unit overhead portion of a first overhead of a first opticaltransport unit frame and to extract information of the first time stampfrom the first overhead of the first optical transport unit frame,wherein the first time stamp was inserted into one of the framealignment overhead portion, the optical channel transporting unitoverhead portion, the optical channel data unit overhead portion, andthe optical channel payload unit overhead portion of the first overheadof a first optical transport unit frame based on at least acharacteristic of the first time stamp, and the characteristic of thefirst time stamp is at least one of a size of the first time stamp, anamount of the first time stamp and a type of the first time stamp; aprocessing module comprising a computer processor to store theinformation of the first time stamp from the first overhead of the firstoptical transport unit frame; a generating module to generate a secondtime stamp based at least in part on the extracted information of thefirst time stamp associated with the first location, wherein the secondtime stamp includes at least part of the extracted information of thefirst time stamp; a transmission module to transmit the second timestamp in a second overhead of a second optical transport unit frame tothe first location via a network to measure a round trip delay of thenetwork.
 13. The system according to claim 12, wherein the generatingmodule generates a second time counter.
 14. The system according toclaim 12, wherein the transmission module associates the second timestamp associated with the second location with a digital wrappingcircuit.
 15. The system according to claim 14, wherein the transmissionmodule associates the second time stamp associated with the secondlocation with an overhead portion of the digital wrapping circuit.
 16. Asystem, comprising: a generating module to generate a first time stampassociated with a first location; a transmission module to transmit thefirst time stamp associated with the first location inserted into one ofa frame alignment overhead portion, an optical channel transporting unitoverhead portion, an optical channel data unit overhead portion, and anoptical channel payload unit overhead portion of a first overhead of afirst optical transport unit frame to a second location via a network,wherein the first time stamp is inserted into one of the frame alignmentoverhead portion, the optical channel transporting unit overheadportion, the optical channel data unit overhead portion, and the opticalchannel payload unit overhead portion of the first overhead of the firstoptical transport unit frame based on at least a characteristic of thefirst time stamp, and the characteristic of the first time stamp is atleast one of a size of the first time stamp, an amount of the first timestamp and a type of the first time stamp; a receiving module to receivea second time stamp inserted in a second overhead of a second opticaltransport unit frame associated with the second location, wherein thesecond time stamp includes at least part of information of the firsttime stamp extracted from the first overhead of the first opticaltransport unit frame; and a processing module comprising a computerprocessor to process the second time stamp associated with the secondlocation to measure a round trip delay of the network.
 17. The systemaccording to claim 16, wherein the generating module generates a timecounter for the first time stamp associated with the first location. 18.The system according to claim 16, wherein the transmission moduleassociates the first time stamp associated with the first location witha digital wrapping circuit.
 19. The system according to claim 18,wherein the transmission module associates the first time stampassociated with the first location with an overhead portion of thedigital wrapping circuit.
 20. The system according to claim 16, whereinthe processing module calculates the round trip delay of the networkbased at least in part on the second time stamp associated with thesecond location.
 21. The system according to claim 16, wherein thenetwork elements at the first location and the second location aresynchronized.
 22. A method, comprising: generating a first time stampassociated with a first location; transmitting the first time stampassociated with the first location inserted into one of a framealignment overhead portion, an optical channel transporting unitoverhead portion, an optical channel data unit overhead portion, and anoptical channel payload unit overhead portion of a first overhead of afirst optical transport unit frame to a second location via a network,wherein the first time stamp is inserted into the one of the framealignment overhead portion, the optical channel transporting unitoverhead portion, the optical channel data unit overhead portion, andthe optical channel payload unit overhead portion of the first overheadof the first optical transport unit frame based on at least acharacteristic of the first time stamp, and the characteristic of thefirst time stamp is at least one of a size of the first time stamp, anamount of the first time stamp and a type of the first time stamp;receiving a first time stamp associated with the first location at thesecond location; extracting information of the first time stamp from thefirst overhead of the first optical transport unit frame; generating asecond time stamp based at least in part on the extracted information ofthe first time stamp associated with the first location, wherein thesecond time stamp includes at least part of the extracted information ofthe first time stamp; transmitting the second time stamp in a secondoverhead of a second optical transport unit frame to the first location;receiving the second time stamp associated with the second location atthe first location; and processing the second time stamp associated withthe second location to measure a round trip delay of the network.
 23. Anon-transitory computer readable storage media comprising code toperform the acts of the method of claim
 1. 24. A non-transitory computerreadable storage media comprising code to perform the acts of the methodof claim
 6. 25. A non-transitory computer readable storage mediacomprising code to perform the acts of the method of claim
 22. 26. Amethod, comprising: a second location receiving a first time stampassociated with a first location inserted into one of a frame alignmentoverhead portion, an optical channel transporting unit overhead portion,an optical channel data unit overhead portion, and an optical channelpayload unit overhead portion of a first overhead of a first opticaltransport unit frame during a first data transmission, wherein the firsttime stamp is inserted into one of the frame alignment overhead portion,the optical channel transporting unit overhead portion, the opticalchannel data unit overhead portion, and the optical channel payload unitoverhead portion of the first overhead of the first optical transportunit frame based on at least a characteristic of the first time stamp,and the characteristic of the first time stamp is at least one of a sizeof the first time stamp, an amount of the first time stamp and a type ofthe first time stamp; extracting information of the first time stampfrom the first overhead of the first optical transport unit frame,generating a second time stamp based at least in part on the extractedinformation of the first time stamp associated with the first location,wherein the second time stamp includes at least part of the extractedinformation of the first time stamp; and transmitting the second timestamp in a second overhead of a second optical transport unit frame tothe first location during a second data transmission wherein the secondtime stamp is used to measure a round trip delay of a network.
 27. Themethod according to claim 26, wherein the first data transmissioncomprises transmitting a first data packet wherein the first data packetcomprises the first time stamp.
 28. The method according to claim 26,wherein the second data transmission comprises transmitting a seconddata packet wherein the second data packet comprises the second timestamp.
 29. The method according to claim 26, wherein the second timestamp is embedded in an overhead portion of a digital wrapping circuit.30. A method, comprising: generating a first time stamp associated witha first location; transmitting the first time stamp associated with thefirst location inserted into one of a frame alignment overhead portion,an optical channel transporting unit overhead portion, an opticalchannel data unit overhead portion, and an optical channel payload unitoverhead portion of a first overhead of a first optical transport unitframe to a second location during a first data transmission via anetwork, wherein the first time stamp is inserted into one of the framealignment overhead portion, the optical channel transporting unitoverhead portion, the optical channel data unit overhead portion, andthe optical channel payload unit overhead portion of the first overheadof the first optical transport unit frame based on at least acharacteristic of the first time stamp, and the characteristic of thefirst time stamp is at least one of a size of the first time stamp, anamount of the first time stamp and a type of the first time stamp;receiving a second time stamp associated with the second location in asecond overhead of a second transport unit frame during a second datatransmission, wherein the second time stamp includes at least part ofinformation of the first time stamp extracted from the first overhead ofthe first transport unit frame; and processing the second time stampassociated with the second location to measure a round trip delay of thenetwork.
 31. The method according to claim 30, wherein the first datatransmission comprises transmitting a first data packet wherein thefirst data packet comprises the first time stamp.
 32. The methodaccording to claim 30, wherein the second data transmission comprisestransmitting a second data packet wherein the second data packetcomprises the second time stamp.
 33. The method according to claim 30,wherein the first time stamp is embedded in an overhead portion of adigital wrapping circuit.